As an environmentally friendly halogen-free flame retardant product which replaces conventional polyvinyl chloride (PVC) materials, and does not use heavy metal compounds such as lead, cadmium, hexavalent chromium, and thus, is safe and less causes earth environmental pollution has come in the spotlight, the demand and importance thereof are gradually expanded.
However, in spite of the domestic and international mandatory environmental regulations, the traditional PVC market does not easily shift to halogen-free flame retardant materials, because the halogen-free flame retardant materials have properties such as high price, not easy workability, a lack of flame retarding technique, and deteriorated flexibility, as compared with PVC.
Particularly, most of the halogen-free products which was crosslinked for increasing thermal resistance, use peroxide crosslinking (chemical crosslinking), electron beam irradiation crosslinking, and water crosslinking methods, and thus, investment in expensive equipment and securing space are required, and these become the factors to inhibit the shift to the halogen-free material product market.
Among the crosslinking methods, the peroxide crosslinking needs expensive crosslinking equipment using a heat medium such as steam, high-frequency and gas, in order to carry out crosslinking by a free radical reaction at high temperature. In addition, in the electron beam irradiation crosslinking, the crosslinking reaction is performed by a radical bonding of high molecular chains produced by high energy electron beam irradiation, which also requires expensive electron beam irradiation equipment. In addition, though the water crosslinking uses a common thermoplastic extruder without investment in expensive equipment for crosslinking, differently from the peroxide crosslinking or the electron beam irradiation crosslinking method, it requires a separate crosslinking process such as immersion in hot water (generally at high temperature of 80° C. or higher) which is separate energy, or exposure to water vapor (steam), which actually requires much more equipment, and high costs for production.
Therefore, due to the problems of the conventional techniques, there has emerged the need to develop a room temperature crosslinking technique capable of producing halogen-free products in general PVC extrusion lines, without investment in CCV (Catenary Continuous Vulcanizing) equipment which is expensive crosslinking equipment, expensive electron beam irradiation equipment, or hot water equipment, thereby developing a halogen-free room temperature crosslinking flame retardant compound material for electrical insulation which is harmless to environment and people, and does not consume extra energy when crosslinking, while satisfying oil resistance, heat resistance, flexibility, electrical insulation and flame resistance.
Accordingly, herein, in order to improve the problems as described above, a room temperature crosslinked type halogen-free flame retardant resin composition has been developed, thereby, providing a novel composition for wires or cables which, after being manufactured into wires or cables by extrusion, may proceed with the crosslinking reaction continuously at room temperature, without a separate crosslinking process, so as to significantly increase long-term mechanical physical properties. Further, the present invention provides a compound material which is a composition for providing the room temperature crosslinked type halogen-free flame retardant resin composition, and a method of preparing the same. Further, the present invention provides a masterbatch for providing the room temperature crosslinked type halogen-free flame retardant resin composition, and a method of preparing the same.